Mono- and Dinuclear Pincer Nickel Catalyzed Activation and Transformation of C–Cl, C–N, and C–O Bonds

Condensation of 2-NH₂C₆H₄P­(Et)­Ph (<b>2</b>) with pyrrole-2-carboxaldehyde generated 2-(C₄H₄N-2′-CHN)­C₆H₄P­(Et)­Ph (<b>3</b>). Treatment of <b>3</b> with NaH and followed by (DME)­NiX₂ (X = Cl, Br) afforded mononuclear pincer nickel complexes [Ni­{2-(C₄H₃N-2′-CHN)­C₆H₄P­(Et)­Ph}­X] (<b>4a</b>, X = Cl; <b>4b</b>, X = Br). Reaction of [2-NH₂C₆H₄P­(Ph)]₂(CH₂)_<i>n</i> (<b>5a</b>, <i>n</i> = 3; <b>5b</b>, <i>n</i> = 4) with pyrrole-2-carboxaldehyde or 5-<i>tert</i>-butyl-1<i>H</i>-pyrrole-2-carbaldehyde formed [2-(C₄H₄N-2′-CHN)­C₆H₄P­(Ph)]₂(CH₂)_<i>n</i> (<b>6a</b>, <i>n</i> = 3; <b>6b</b>, <i>n</i> = 4) and [2-(5′-<i>t</i>BuC₄H₃N-2′-CHN)­C₆H₄P­(Ph)]₂(CH₂)₄ (<b>6c</b>). Respective treatment of <b>6a</b>–<b>c</b> with NaH followed by (DME)­NiX₂ (X = Cl, Br) gave the dinuclear nickel complexes [Ni­{2-(5′-RC₄H₂N-2′-CHN)­C₆H₄P­(Ph)}­X]₂(CH₂)_<i>n</i> (<b>7a</b>, R = H, X = Cl, <i>n</i> = 3; <b>7b</b>, R = H, X = Cl, <i>n</i> = 4; <b>7c</b>, R = H, X = Br, <i>n</i> = 4; <b>7d</b>, R = <i>t</i>Bu, X = Cl, <i>n</i> = 4). Catalysis of the complexes for the activation and transformation of C–Cl, C–N, and C–O bonds was evaluated. Complex <b>7c</b> exhibited excellent catalytic activity in the cross-coupling of aryl chlorides or aryltrimethylammonium iodides with arylzinc reagents as well as of aryl sulfamates with aryl Grignard reagents. The dinuclear nickel complexes <b>7b</b>–<b>d</b> showed higher catalytic activity than the mononuclear complexes in each type of reaction

Nickel-Catalyzed Cross-Coupling of Aryl Fluorides and Organozinc Reagents

Ni­(PCy₃)₂Cl₂ was demonstrated to effectively catalyze cross-coupling of aryl fluorides and organozinc reagents. Both electron-poor and -rich aryl fluorides can react effectively with nucleophiles including aryl-, methyl-, and benzylzinc chlorides. A wide range of substituents and functional groups are tolerated. In the presence of a directing group, PhC­(O), the reaction is selective for cleavage of the C–F bond <i>ortho</i> to the carbonyl substituent in a difluoroarene

Palladium-Catalyzed Coupling of Azoles or Thiazoles with Aryl Thioethers via C–H/C–S Activation

Palladium-catalyzed cross-coupling via the C_sp²–S bond activation of aryl thioethers and the C–H bond activation of azoles or thiazoles was carried out. Electron-deficient and -rich aryl methyl thioethers and diaryl thioethers can be employed as the coupling partners and the reaction tolerates a range of functional groups including MeO, CF₃, CN, PhCO, CONEt₂, and Py groups

Scarabaeus sp.

N-Heterocyclic carbene-based pincer nickel complexes were synthesized and characterized. These complexes efficiently catalyze cross-coupling of aryl Grignard reagents with aryl chlorides or fluorides under mild conditions

Nickel-Catalyzed Cross-Coupling of Allyl Alcohols with Aryl- or Alkenylzinc Reagents

Nickel-catalyzed cross-coupling of allyl alcohols with aryl- and alkenylzinc chlorides through C–O bond cleavage was performed. Reaction of (<i>E</i>)-3-phenylprop-2-en-1-ol and 1-aryl-prop-2-en-1-ols with aryl- or alkenylzinc chlorides gave linear cross-coupling products. Reaction of 1-phenyl- or 1-methyl-substituted (<i>E</i>)-3-phenylprop-2-en-1-ol with aryl- or alkenylzinc chlorides resulted in 3-aryl/alkenyl-substituted (<i>E</i>)-(prop-1-ene-1,3-diyl)­dibenzenes or 3-aryl/alkenyl-substituted (<i>E</i>)-(but-1-enyl)­benzene. Reaction of allyl alcohol with <i>p</i>-Me₂NC₆H₄ZnCl resulted in a mixture of normal coupling product 4-allyl-<i>N,N</i>-dimethylaniline and its isomerized product <i>N,N</i>-dimethyl-4-(prop-1-en-1-yl)­aniline

Nickel-Catalyzed Amination of Aryl 2‑Pyridyl Ethers via Cleavage of the Carbon–Oxygen Bond

Reaction of aryl 2-pyridyl ethers with amines was carried out via Ni-catalyzed C–O_Py bond cleavage, giving aniline derivatives in reasonable to excellent yields. Both electron-rich and electron-poor aryl 2-pyridyl ethers and a wide range of amines can be used in the transformation. The method provides a conversion way for the 2-pyridyloxy directing group in the C–H bond functionalization reactions

Transition-Metal-Free Cross-Coupling of Aryl and Heteroaryl Thiols with Arylzinc Reagents

Cross-coupling of (hetero)­arylthiols with arylzinc reagents via C–S cleavage was performed under transition-metal-free conditions. The reaction displays a wide scope of substrates and high functional-group tolerance. Electron-rich and -deficient (hetero)­arylthiols and arylzinc reagents can be employed in this transformation. Mg²⁺ and Li⁺ ions were demonstrated to facilitate the reaction

One-Pot Green Synthesis of High Quantum Yield Oxygen-Doped, Nitrogen-Rich, Photoluminescent Polymer Carbon Nanoribbons as an Effective Fluorescent Sensing Platform for Sensitive and Selective Detection of Silver(I) and Mercury(II) Ions

This work reports on a facile, economical, and green preparative strategy toward water-soluble, fluorescent oxygen-doped, nitrogen-rich, photoluminescent polymer carbon nanoribbons (ONPCRs) with a quantum yield of approximately 25.61% by the hydrothermal process using uric acid as a carbon–nitrogen source for the first time. The as-prepared fluorescent ONPCRs showed paddy leaf-like structure with 80–160 nm length and highly efficient fluorescent quenching ability in the presence of mercury­(II) (Hg²⁺) or silver (Ag⁺) ions due to the formed nonfluorescent metal complexes via robust Hg²⁺-O or Ag⁺-N interaction with the O and N of fluorescent ONPCRs, which allowed the analysis of Hg²⁺ and Ag⁺ ions in a very simple method. By employing this sensor, excellent linear relationships existed between the quenching degree of the ONPCRs and the concentrations of Hg²⁺ and Ag⁺ ions in the range of 2.0 nM to 60 μM and 5.0 nM to 80 μM, respectively. By using ethylenediaminetetraacetate and ammonia as the masking agent of Hg²⁺ and Ag⁺ ions, respectively, Hg²⁺ or Ag⁺ ions were exclusively detected in coexistence with Ag⁺ or Hg²⁺ ions with high sensitivity, and the detection limits as low as 0.68 and 1.73 nM (3σ) were achieved, respectively, which also provided a reusable detection method for Hg²⁺ and Ag⁺ ions. Therefore, the easily synthesized fluorescent ONPCRs may have great potential applications in the detection of Hg²⁺ and Ag⁺ ions for biological assay and environmental protection

Rh(III)-Catalyzed C–H Allylation of Aromatic Ketoximes with Vinylaziridines

The Rh(III)-catalyzed reaction of aromatic ketoximes with 2-vinylaziridines affords ortho-allylation products of the phenyl rings of aromatic ketoximes in moderate to excellent yields. The reaction requires 0.5 equiv of NaOAc as a base and occurs under mild conditions. The protocol exhibits ortho-monoallylation selectivity, wide scope of substrates, and good compatibility of functional groups

Cross-Coupling of Aryltrimethylammonium Iodides with Arylzinc Reagents Catalyzed by Amido Pincer Nickel Complexes

The cross-coupling reaction of aryltrimethylammonium iodides with aryl- or heteroarylzinc chlorides catalyzed by amido pincer nickel complexes was performed. The reaction requires low catalyst loading and displays broad substrate scope